(a) Field of the Invention
The present invention relates to a method for preparing cerium carbonate, a cerium carbonate powder, and a method for preparing a cerium oxide powder using the same. More specifically, the present invention relates to a method for preparing cerium carbonate which enables preparation of hexagonal cerium carbonate by a simplified process, a cerium carbonate powder prepared thereby, and a method for preparing a cerium oxide powder using the same.
(b) Description of the Related Art
Cerium oxide is high functional ceramic material widely used as a catalyst, phosphor, cosmetics, abrasive, etc., and, recently, it is spotlighted as an abrasive for CMP (Chemical Mechanical Polishing) process in the field of semiconductor device.
The cerium oxide is generally prepared by a liquid-phase method, a gas-phase method or a solid-phase method.
According to the liquid-phase method, a pH controlling agent such as ammonia is added to starting material, i.e., trivalent or tetravalent cerium salt to directly prepare cerium oxide from cerium salt. Although this method is economical because raw material cost and equipment cost is comparatively low, it is difficult to control particle growth because reaction between starting materials easily occurs from nucleation stage. And, if fine cerium oxide prepared by the liquid-phase method is used as an abrasive, polishing rate is low thus disadvantageous for a continuous process and decreasing productivity.
According to the gas-phase method, a cerium metal salt precursor is vaporized and then combined with oxygen, etc. to directly prepare cerium oxide. This method includes flame combustion decomposition, gas condensation decomposition, plasma vaporization, laser vaporization, etc. However, this method has difficulty in terms of massification because costs of the cerium metal salt precursor and equipment are high, and the study thereof is still under progress.
Meanwhile, according to the solid-phase method, precursor material is sintered at high temperature to prepare cerium oxide. As the precursor, cerium carbonate is widely used, and the property and shape of cerium oxide change according to the kind and shape of cerium carbonate. Thus, in order to control the property, shape, abrasiveness, etc. of cerium oxide abrasive, it is required to control the kind or shape of precursor cerium carbonate precursor.
However, a method for preparing cerium carbonate with controlling the kind or shape of cerium carbonate by a simplified process has not been adequately developed yet, and particularly, there is a continued demand for a method capable of preparing hexagonal cerium carbonate by more simplified process.